36 - Miter Trimmer, страница 27

36 - Miter Trimmer, страница 27

TECHNIQUE

Biscuit

^^ ■ A football-shaped "biscuit" can also be used to strengthen a miter joint. Here again, the biscuit provides a large glue surface that gives the joint its strength. But this time, the biscuit is hidden inside a slot that's cut in the mitered ends of each workpiece.

Although you can cut this slot with a plate joiner and then glue in a special biscuit, there's another way to accomplish the same thing. Just use a slot cutter in a table-mounted router and make your own biscuit.

guide. An easy way to do this is to use a square scrap of plywood as a guide. The idea is to use two adjoining edges of the guide to direct the mitered workpieces into the bit, see drawing and detail 'a.' Note: Clamping two scraps to the router table keeps the pieces from kicking to the side.

To center each slot on the end of the workpiece, position the guide so a line drawn between two opposite corners passes through the center of the bit, see drawing. The distance from the corner to

the bit equals half the length of the angled end of the miter.

biscuits. All that's left is to make the biscuits. To do this, draw a series of overlapping circles that match the diameter of the slot cutter, see detail 'b.' Then cut the biscuits to size. A

orient diagonal .ine toward center of 5lot cutter

NOTE: cut all slots with workpieces face up

ly thickness stock to fit slot

compass

compass to match diameter of slot cutter

scrap

guide

Mechanical Fasteners

Wood splines and plugs aren't the only way to strengthen a miter joint. There are also a number of different mechanical fasteners available that you can use to reinforce a miter joint, see photos below.

Installing these fasteners is easy. With the mitered pieces glued together, just use a hammer to tap the fas

teners into the back of the miter joint. (As a rule, use at least two fasteners on each corner.)

The only drawback to these fasteners is they tend to crumple if 3'ou drive them into hardwood which can cause the wood (or the joint) to split. So it's best to use them only for softwood. For sources of fasteners, see page 31.

• Corrugated Nails. The ridges on these corrugated nails hold the mitered corner of the frame tightly together.

Chevrons. Once these chevrons are tapped in place, the spring steel wings help strengthen the mitered corner.

Tack Plates. The sharp, angled claws on the bottom of these metal tack plates help reinforce the miter joint.

No. 36

ShopNotes

27

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